1. Field of the Invention
The present invention relates to a power control technique for a network system in which a plurality of devices, such as computers, are connected over a network.
2. Description of the Related Art
Recently, as the performance of computers is enhanced, the consumed power becomes greater. In a machine room where a plurality of computers are sited, an increase in consumed power is becoming a significant problem. In general, at the time of designing a machine room, the maximum suppliable power value (the sum of the values of power that can be supplied to the individual computers) is set to the sum of the rated power values of the individual computers. However, actually, each computer does not consistently need a rated power value, it is rare for all of the computers to use the rated power value at a time. Therefore, setting the maximum suppliable power value to the sum of the rated power values of the individual computers brings about a problem such that the power equipment in the machine room becomes excessive.
To achieve the problem, Unexamined Japanese Patent Application KOKAI Publication No. 2006-11793 (hereinafter called “Patent Document 1”) discloses the following technique. The Patent Document 1 discloses the technique of providing a specific computer with a master management module which processes a power increase request sent from each computer to adequately distribute the limited power according to the operational state of each computer in a computer system including a plurality of computers. Each computer sends a power increase request to the master management module when determining that consumed power needs to be increased based on the operational state of the computer itself. Upon reception of the power increase request, the master management module determines whether the sum of the consumed powers of the individual computers exceeds the maximum suppliable power value if the consumed power of the requesting computer is increased. When the master management module determines that the sum of the consumed powers of the individual computers does not exceed the maximum suppliable power value, the master management module sends an increase enable notification to the requesting computer. When the master management module determines that the sum of the consumed powers of the individual computers exceeds the maximum suppliable power value, on the other hand, the master management module sends an increase disable notification to the requesting computer. When receiving the increase enable notification, the requesting computer increases the consumed power of the computer itself. When receiving the increase disable notification, the requesting computer sends a power increase request to the master management module again after a predetermined time. Apparently, the technique disclosed in Patent Document 1 can adequately distribute the limited power according to the operational state of each computer.
However, the technique disclosed in Patent Document 1 allows a single computer having the master management module mounted therein to intensively process the power increase request. When the computer fails, therefore, power control cannot be carried out at all, resulting in a low reliability. While multiplexing of computers having the master management modules mounted therein can overcome the above problem, the configuration becomes complex.